Automated substrate processing system

ABSTRACT

A substrate handling apparatus includes a transfer arm having a substrate support. The apparatus includes at least one image acquisition sensor configured to acquire images of a substrate supported by the substrate support. In addition, the apparatus includes a controller coupled to the image acquisition sensor and configured to control the image acquisition sensor to acquire at least one image of the substrate supported on the substrate support. The controller is further configured to receive the images acquired by the image acquisition sensor and to determine an initial position of the substrate based on the acquired images. The controller is further coupled to the substrate support to control movement thereof to move the substrate to a new position based on the substrate&#39;s initial position. The apparatus also can be used to determine a substrate identification and to detect certain substrate defects either before or after processing the substrate in a thermal processing chamber. A method of positioning a substrate on a transfer arm also is disclosed.

RELATED APPLICATION

“This is a continuation of co-pending application (s) Ser. No.09/082,413 filed on May 20, 1998, U.S. Pat. No. 6,215,897.”

The present application is related to co-pending U.S. patent applicationSer. No. 08/946,922, filed Oct. 8, 1997 and entitled“Modular On-LineProcessing System,” as well as the following U.S. patent applicationswhich are being filed concurrently with this application: (1) “Methodand Apparatus for Substrate Transfer and Processing” [attorney docket2519/US/AKT (05542/235001)]; (2) “Isolation Valves,” [attorney docket2157/US/AKT (05542/226001)]; (3) “Multi-Function Chamber For A SubstrateProcessing System,” [attorney docket 2712/US/AKT (05542/268001)]; (4)“Substrate Transfer Shuttle Having a Magnetic Drive,” [attorney docket2638/US/AKT (05542/264001)]; (5) “Substrate Transfer Shuttle,” [attorneydocket 2688/US/AKT (05542/265001)]; (6) “In-Situ Substrate TransferShuttle,” [attorney docket 2703/US/AKT (05542/266001)]; and (7) “ModularSubstrate Processing System,” [attorney docket 2311/US/AKT(05542/233001)].

The foregoing patent applications, which are assigned to the assignee ofthe present application, are incorporated herein by reference in theirentirety.

BACKGROUND

The present invention relates generally to an automated substrateprocessing system, and, in particular, to techniques for improvingsubstrate alignment and detecting substrate defects using imageacquisition sensors.

Glass substrates are being used for applications such as active matrixtelevision and computer displays, among others. Each glass substrate canform multiple display monitors each of which contains more than amillion thin film transistors.

The processing of large glass substrates often involves the performanceof multiple sequential steps, including, for example, the performance ofchemical vapor deposition (CVD) processes, physical vapor deposition(PVD) processes, or etch processes. Systems for processing glasssubstrates can include one or more process chambers for performing thoseprocesses.

The glass substrates can have dimensions, for example, of 550 by 650 mm.The trend is toward even larger substrate sizes, such as 650 mm by 830mm and larger, to allow more displays to be formed on the substrate orto allow larger displays to be produced. The larger sizes place evengreater demands on the capabilities of the processing systems.

Some of the basic processing techniques for depositing thin films on thelarge glass substrates are generally similar to those used, for example,in the processing of semiconductor wafers. Despite some of thesimilarities, however, a number of difficulties have been encountered inthe processing of large glass substrates that cannot be overcome in apractical way and cost effectively by using techniques currentlyemployed for semiconductor wafers and smaller glass substrates.

For example, efficient production line processing requires rapidmovement of the glass substrates from one work station to another, andbetween vacuum environments and atmospheric environments. The large sizeand shape of the glass substrates makes it difficult to transfer themfrom one position in the processing system to another. As a result,cluster tools suitable for vacuum processing of semiconductor wafers andsmaller glass substrates, such as substrates up to 550 by 650 mm, arenot well suited for the similar processing of larger glass substrates,such as 650 mm by 830 mm and above. Moreover, cluster tools require arelatively large floor space.

Similarly, chamber configurations designed for the processing ofrelatively small semiconductor wafers are not particularly suited forthe processing of these larger glass substrates. The chambers mustinclude apertures of sufficient size to permit the large substrates toenter or exit the chamber. Moreover, processing substrates in theprocess chambers typically must be performed in a vacuum or under lowpressure. Movement of glass substrates between processing chambers,thus, requires the use of valve mechanisms which are capable of closingthe especially wide apertures to provide vacuum-tight seals and whichalso must minimize contamination.

Furthermore, relatively few defects can cause an entire monitor formedon the substrate to be rejected. Therefore, reducing the occurrence ofdefects in the glass substrate when it is transferred from one positionto another is critical. Similarly, misalignment of the substrate as itis transferred and positioned within the processing system can cause theprocess uniformity to be compromised to the extent that one edge of theglass substrate is electrically non-functional once the glass has beenformed into a display. If the misalignment is severe enough, it even maycause the substrate to strike structures and break inside the vacuumchamber.

Other problems associated with the processing of large glass substratesarise due to their unique thermal properties. For example, therelatively low thermal conductivity of glass makes it more difficult toheat or cool the substrate uniformly. In particular, thermal losses nearthe edges of any large-area, thin substrate tend to be greater than nearthe center of the substrate, resulting in a non-uniform temperaturegradient across the substrate. The thermal properties of the glasssubstrate combined with its size, therefore, makes it more difficult toobtain uniform characteristics for the electronic components formed ondifferent portions of the surface of a processed substrate. Moreover,heating or cooling the substrates quickly and uniformly is moredifficult as a consequence of its poor thermal conductivity, therebyreducing the ability of the system to achieve a high throughput.

Automated substrate processing systems typically include one or moretransfer mechanisms, such as robotic devices or conveyors, fortransferring substrates between different parts of the processingsystem. For example, one transfer mechanism may transfer substrates oneat a time between a cassette and a load lock chamber. A second transfermechanism may transfer substrates between the load lock chamber and thevacuum chamber where the substrate is subjected to various processingsteps.

Each time a substrate is transferred automatically from to or from achamber, the substrate may become misaligned with respect to componentswithin the chamber or with respect to other system components. Ingeneral, alignment errors accumulate as the substrate is transferredthrough the processing system. If the degree of misalignment is toogreat, the quality of the processed substrate can become significantlydegraded, or the substrate might break. When a substrate breaks inside avacuum chamber, the chamber must be opened and exposed to atmosphericpressure, the chamber must be cleaned, and the chamber must be pumpedback down to a sub-atmospheric pressure suitable for processing. Such aprocedure may take up to twenty-fours to complete, thereby significantlyreducing the time during which the system can be used to processsubstrates.

SUMMARY

In general, in one aspect, a substrate handling apparatus includes atransfer arm or conveyor having a substrate support, and at least oneimage acquisition sensor configured to acquire images of a substratesupported by the substrate support. The substrate handling apparatusalso can include a controller coupled to the image acquisition sensorand configured to control the image acquisition sensor to acquire one ormore images of the substrate supported on the substrate support. Thecontroller is further configured to receive the image(s) acquired by theimage acquisition sensors and to determine an initial position of thesubstrate based on the acquired image(s). The controller also is coupledto the substrate support to control movement thereof to move thesubstrate to a new position based on the substrate's initial position.

In another aspect, a method of positioning a substrate includessupporting the substrate on a substrate support of a transfer arm andacquiring at least one image of the substrate supported on the substratesupport. The method further includes determining an initial position ofthe substrate based on the acquired image(s) and moving the substratesupport based on the initial position to adjust for a misalignment ofthe substrate.

Various implementations include one or more of the following features.The substrate handling apparatus can include an automatic atmospheric orvacuum transfer arm or conveyor that includes one or more blades tosupport the substrate. The image acquisition sensor(s) can include anarray of charge coupled devices or other cameras. Each image acquisitionsensor can be controlled to take one or more images of the substrate.

The substrate handling apparatus can include a light source to enhance aquality of images acquired by the image acquisition sensor(s). In someimplementations, the light source can include an incandescent lightsource or a strobe lamp.

The substrate handling apparatus can be configured so that the acquiredimage(s) includes a portion of at least one edge of the substrate. Theacquired images can include respective portions of adjacent edges of thesubstrate or a corner of the substrate.

The controller can be configured to apply an edge detection or otherspecific template algorithm to the acquired images. An initial angularorientation of the substrate can be determined based on the acquiredimage(s). The apparatus can include a memory associated with thecontroller, wherein the memory stores ideal information indicative of anideal substrate position, and wherein the controller is furtherconfigured to compare the initial substrate position to the idealsubstrate position.

In addition, the controller can be configured to control movement of thesubstrate support to adjust the angular orientation or the linearhorizontal translation of the substrate in response to determining thesubstrate's initial angular orientation. The angular orientation and thelinear horizontal translation of the substrate support can be controlledto correct a misalignment of the substrate based on the substrate'sinitial position. In some implementations, the substrate is transferredto a processing chamber or to a load lock chamber after moving thesubstrate support to adjust for the misalignment. Additionally, in someimplementations, the substrate support is moved to adjust for themisalignment after removing the substrate from a processing chamber orafter removing the substrate from a load lock chamber.

If the substrate includes a substrate identification, one of theacquired images can capture the identification, and a characterrecognition algorithm can be performed to interpret the substrateidentification.

In some implementations, the substrate support is translated verticallywhile the substrate is supported thereon, and an image that includessubstantially an entire surface of the substrate can be acquired. Adetermination can be made as to whether defects exist in the substratebased on one or more images of the substrate surface. The defectdetection can be performed either before or after processing of thesubstrate.

Various implementations include one or more of the following advantages.Large substrates, such as glass substrates, used during the manufactureof flat panel displays and liquid crystal displays (LCDs) can be alignedand positioned with greater accuracy. The rate of substrate breakage canbe reduced by detecting when a substrate is misaligned and repositioningthe substrate. The time during which substrates can be processed can beincreased, and the throughput rate and processing yield similarly can beincreased. In addition, the quality of the substrate process can beimproved by reducing the number of times the system must be opened andexposed to atmospheric conditions.

Furthermore, the same image acquisition sensor that is used fordetecting misalignment of substrates can be used for detecting asubstrate identification inscribed on the substrate. Similarly, such animage acquisition sensor can be used to detect defects in the substratesso that the damaged substrates can be removed from further processing.Therefore, in various implementations, the image acquisition sensors canprovide multiple advantages, thereby increasing efficiency and reducingthe overall cost of substrate processing.

Other features and advantages will become apparent from the followingdescription, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic top view of a substrate processing systemaccording to the invention.

FIG. 2 is a block diagram illustrating an example of substrate movementthrough the substrate processing system.

FIG. 3 is a flow chart of an exemplary method of processing a substratein the substrate processing system.

FIG. 4 is an elevated view of an automatic vacuum transfer arm.

FIG. 5 is an elevated side view, not drawn to scale, of an automaticatmospheric transfer arm with an image acquisition system according toone implementation of the invention.

FIG. 6 is a top view of a transfer head of the atmospheric transfer arm.

FIG. 7 shows further details of the implementation of FIG. 5.

FIG. 8 is a flow chart of a method according to one implementation ofthe invention.

FIG. 9 is an elevated side view of a transfer arm with an imageacquisition system according to a second implementation of theinvention.

FIG. 10 shows further details of the implementation of FIG. 9.

FIG. 11 is an elevated side view of a transfer arm with an imageacquisition system according to a third implementation of the invention.

FIG. 12 shows further details of the implementation of FIG. 11.

FIG. 13 is an elevated side view of a transfer arm illustratingadditional features of an image acquisition system according to animplementation of the invention.

FIGS. 14A and 14B are elevated side views of a transfer arm illustratingyet further features of an image acquisition system according to animplementation of the invention.

FIG. 15 is an elevated view of the vacuum transfer arm with an imageacquisition system according to one implementation of the invention.

FIG. 16 is a diagrammatic top view of another substrate processingsystem in which image acquisition sensors can be used according to theinvention.

DETAILED DESCRIPTION

As shown in FIG. 1, a system 10 for processing a glass or similarsubstrate 11 includes an atmospheric cassette load station 12, two loadlock chambers 14, 16, five substrate processing chambers 18-26 and atransfer chamber 27. The substrate processing chambers 18-26 caninclude, for example, a physical vapor deposition (PVD) chamber, achemical vapor deposition (CVD) chamber, a preheat chamber, and an etchchamber.

Each load lock chamber 14, 16 includes two doors, one opening into thetransfer chamber 27 and the other opening into to the atmospherecassette load station 12. To load a substrate into the system, it isplaced in one of the load lock chambers 14, 16 from the atmosphericside. Then the load lock chamber 14 (or 16) is evacuated, and thesubstrate is unloaded from the transfer chamber side.

The atmospheric cassette load station 12 includes an automaticatmospheric transfer arm or robot 36 and four cassettes 28-34 whichcontain processed and unprocessed substrates. The transfer chamber 27includes an automatic vacuum transfer arm or robot 38 for transferringsubstrates into and out of load lock chambers 14, 16 and processingchambers 18-26. In operation, the atmospheric cassette load station 12is at atmospheric pressure, and each of the processing chambers 18-26and transfer chamber 27 is maintained at a sub-atmospheric pressure. Theload lock chambers 14, 16 are at atmospheric pressure when a substrateis being transferred to or from atmospheric cassette load station 12,and they are at a sub-atmospheric pressure when a substrate is beingtransferred to or from the transfer chamber 27.

Referring to FIG. 4, the vacuum transfer arm 38 has a base 80 that issealed against the bottom of the transfer chamber 27 (FIG. 1) andincludes a pair of arms 81, 82 which can extend and retract as indicatedby the double-headed arrow 83 by pivoting about respective axes 84-87.The substrate 11 is supported on a support head 88 that includes twosupport blades 90, 92. The vacuum transfer arm 38 also can rotate aboutan axis 94.

Referring to FIGS. 5 and 6, the atmospheric transfer arm 36 includes atransfer head 37 with two thin support blades 72, 74 for supporting asubstrate 11. The transfer head 37 has arm segments 76, 78 which can berotated about multiple pivot axes to position the substrate 11, forexample, in a load lock chamber with high accuracy. The transfer head 37also can move up and down. Additionally, the atmospheric transfer arm 36can slide back and forth along a linear track inside the atmosphericcassette load station 12

The positions and orientations of the atmospheric transfer arm 36, aswell as the vacuum transfer arm 38, are controlled and recorded amicroprocessor-based controller 35. For example, the transfer arms 36,38 can be driven by servo motors whose positions are controlled by thecontroller 35.

Referring to FIGS. 2 and 3, in one implementation which can be used in aliquid crystal display (LCD) fabrication process, a glass substrate maybe processed in system 10 as follows. The atmospheric transfer arm 3-6transfers the substrate from the atmospheric cassette load station 12 tothe load lock chamber 14 (step 40). The load lock chamber is pumped downto a pressure of about 10⁻⁵ Torr (step 41). A first processing chamber,such as the chamber 22, is pre-heated (step 43). The vacuum transfer arm38 unloads the substrate from the load lock chamber 14 (step 42) andtransfers the substrate to a pre-heat of first processing chamber 22(step 44). The processing chamber 22 is pumped down to a pressure ofabout 10⁻⁸ Torr and the substrate is preheated to an initial temperatureof about 200-400°C. (step 46). The vacuum transfer arm 38 unloads thesubstrate from the processing chamber 22 (step 47) and transfers thesubstrate to another processing chamber, such as the chamber 20, forfurther processing (step 48). The processing chamber 20 is pumped downto a pressure of about ¹⁰⁻Torr and the substrate is processed bydepositing, such as by PVD or CVD, a layer of titanium, aluminum,chromium, tantalum, indium-tin-oxide (ITO), or the like, on thesubstrate (step 49). The substrate may be processed in one or more otherprocessing chambers, if necessary (step 50). After the substrate isfinally processed, the vacuum transfer arm 38 unloads the substrate fromthe final processing chamber (step 51) and transfers the substrate tothe load lock chamber 14 (step 52). The load lock chamber 14 ispressurized back to atmospheric pressure (step 53). The atmospherictransfer arm 36 then transfers the substrate from the load lock chamber14 to a cassette in the atmospheric cassette load station 12 (step 54).

To help prevent significant substrate misalignment, the processingsystem 10 includes one or more image acquisition sensors, positioned toprovide information relating to the orientation and position of asubstrate 11, as described in greater detail below. The acquiredinformation can be used by the controller 35 to adjust the positionand/or orientation of the substrate 11.

Referring again to FIG. 5, an image acquisition sensor, such as a camera100, is positioned in a fixed location with respect to the base 98 ofthe atmospheric transfer arm 36. The camera 100 can be mounted, forexample, on a metal bracket or flange 99 attached to the base 98 of thetransfer arm 36. In the illustrated implementation, the camera 100 ispositioned slightly below the support blades 72, 74. The camera 100 iscoupled to the controller 35 which controls the operation of the camera.Signals corresponding to images acquired or captured by the camera 100can be sent to the controller 35 for processing, as explained below.

Referring to FIG. 7, in one implementation, the camera 100 includes alens having a focal plane 102 and an array of charge coupled devices(CCDs) 104 forming an N×M array of pixels 106. A typical substrate 11 ison the order of one square meter. Substrates having other dimensions,however, also can be used. The edges of the substrate 11, such as theedge 101A, can be substantially straight, beveled or rounded. In oneimplementation, the camera 100 is approximately 100-200 millimeters (mm)from the bottom surface of the substrate 11. In other implementations,the camera 100 can be positioned closer to or further from the substrate11. The shape and size of the camera lens and the size of the COD array104 are selected to provide a post-processing resolution of at leastapproximately one mm per meter, in other words, a resolution of at leastabout 1/1000th.

Referring to FIG. 8, the atmospheric transfer arm 36 supports thesubstrate 11 for transfer between the atmospheric cassette load station12 and, for example, the load lock chamber 14 (step 110). When thesubstrate 11 is supported by the blades 72, 74 and the transfer head 37is controlled by the controller 35 to position the blades 72, 74 in apredetermined position, a portion of a side edge 101A of the substrate11 is within the camera's view. As indicated by step 112, the controller35 generates a signal causing the camera 100 to capture or acquire theimage in the CCD array 104. Signals representing the captured image fromthe CCD array 104 are transferred to a frame grabber or memory array 96associated with the controller 35 (step 114). The controller 35 thenperforms any one of several edge detection algorithms on the capturedimage data (step 116). The edge detection algorithm can include an edgeenhancement feature. Pixels 106 receiving light reflected by ortransmitted through the edge 101A will store different signal levelscompared to pixels receiving light reflected by or transmitted throughthe body of the substrate or transmitted through the air. The controller35 calculates the angular orientation of the substrate 11 in the X-Yplane (FIG. 7) and the position of the substrate along the Y-axis basedon detection of the substrate edge (step 118). The calculated values arecompared to an ideal substrate orientation and ideal position stored ina non-volatile memory 97 associated with the controller 35 (step 120).Based on the comparison, the controller 35 can control the transfer arm36 to rotate the substrate 11 and/or translate it linearly along theY-axis to correct any detected misalignment of the substrate 11 (step122). The transfer arm 36 then can transfer the substrate 11 to thecassette load station 12 or the selected load lock chamber, asappropriate (step 124).

FIGS. 9-10 illustrate another implementation in which a single camera100A is positioned so that when-the substrate 11 is supported by theblades 72, 74 and the blades are in a predetermined position, a portionof the corner 105A of the substrate 11 is within the camera's view 102A.Thus, a single camera 100A can capture a portion of at least twoadjacent edges of the substrate 11, and misalignment of the substrate 11along both the X-axis and the Y-axis can be detected. The controller 35uses an edge detection algorithm to analyze the captured image anddetermine the orthoganol lines representing the adjacent edges 101A,101B which form the corner 105A. The controller 35 then uses a cornerdetection algorithm in which, for example, it calculates the point ofintersection of the lines corresponding to the edges 101A, 101B. Thepoint of intersection corresponds to the location of the substratecorner 105A. The memory 97 also stores information indicative of thenominal size of the substrate 11. Based on the nominal size of thesubstrate 11 and the calculated point of intersection, the center pointof the substrate in the X-Y plane can be calculated. Additionally, thelines corresponding to the edges 101A, 101B can be used to calculate theangular orientation of the substrate 11. The calculated values for thecenter of the substrate and its angular orientation are compared toideal values stored in the memory 97. Based on the comparison, thesubstrate 11 can be rotated or moved along the X-axis, the Y-axis, orboth to adjust the position of the substrate 11 and bring it closer toan ideal position. The angular orientation of the substrate 11 also canbe adjusted based on the results of the comparison.

Positioning a camera to capture an image of the substrate corner 105A isadvantageous because it allows the angular orientation of the substrate11, as well as its position in the X-Y plane, to be determined. However;in some situations, a camera positioned as illustrated in FIGS. 9-10 maynot capture as much useful information as desired. For example,depending on the initial position of the substrate 11 with respect tothe camera 100A, only a relatively small percentage of pixels 106A ofthe CCD array 104A may detect light signals reflected by or transmittedthrough the edge 101A.

A third implementation, incorporating multiple cameras 100B, 100C, isillustrated in FIGS. 11-12. The cameras 100B, 100C are positioned sothat when the substrate 11 is supported by the blades 72, 74 and theblades are in a predetermined position, adjacent sides 101, 101B of thesubstrate 11 are within the view of the respective cameras 100B, 100C.Using images from two or more cameras allows the controller 35 to obtainbetter resolution and to determine the angular orientation and positionof the substrate 11 in the X-Y plane more accurately. The controller 35then can correct any detected misalignment of the substrate 11 with moreprecision. In one implementation, the time allotted for the measurementof the substrate position and orientation is in the range of a fractionof a second.

In some situations, the substrate 11 vibrates slightly while resting onthe blades 72, 74. Such vibrations, on the order of several millimetersor less, can occur even when movement of the transfer arm 36 is stoppedmomentarily to permit the alignment measurements to be made. Thevibrations can result in slightly blurred images captured by the camerasas the substrate 11 goes in and out of focus. Moreover, the pixel(s) 106which capture the image of a particular spot on the substrate 11 canvary depending on the vibrations of the substrate. The vibrations,therefore, can adversely affect the system's calculation of thesubstrate misalignment and can cause the controller 35 to overcompensateor undercompensate for a perceived misalignment.

To compensate for substrate vibrations more accurately, the cameras,such as the camera 100, can include an automatic focus feature.Alternatively, to further reduce the cost, the controller 35 can controleach camera, such as the camera 100, to capture multiple images within asmall time frame. In one implementation, for example, the cameras arecontrolled to capture multiple images at the rate of approximately 60Hertz (Hz). The controller 35 then determines an average signal for eachpixel 106 based on the captured images. The average signals then can beused to calculate a nominal, or static, substrate position andorientation. In addition, the camera lens can have a depth of focusdesigned to cover the expected amplitude of substrate vibration.

To increase the resolution of the captured images even further, thecontroller 35 can be programmed to use any one of several sub-pixelprocessing techniques. In one implementation, for example, sub-pixelprocessing provides one-tenth pixel resolution.

In some situations, ambient light is sufficient to allow the controller35 to detect the contrast in the pixels of the captured images so thatthe position of the edges, such as the edge 101A, can be determined. Inother situations, however, one or more light sources 95 (FIG. 5) can beprovided to enhance the contrast and improve the results of the edgedetection algorithm. In one implementation, for example, an incandescentlight source is provided on the same side of the substrate 11 as thecamera 100. In another implementation, a strobe lamp is used as thelight source 95. The strobe lamp can be used to freeze the imageacquired by the camera 100. Such a feature can be particularly useful ifthe frequency of substrate vibration is relatively high.

The cameras, such as the camera 100, can be used for other or additionalpurposes as well. Referring to FIG. 13, a glass substrate 11A includes asubstrate identification 107 along a surface adjacent one of its sideedges 109. The substrate identification 107 can be etched, engraved orotherwise inscribed on the substrate 11A. In one implementation, thesubstrate identification 107 includes alpha-numeric symbols. The camera100 is positioned so that when the substrate 11A is supported by theblades 72, 74 and the transfer head 37 is controlled by the controller35 to position the blades 72, 74 in a predetermined position, thesurface of the substrate 11A containing the substrate identification 107is within the view of the camera 100. One or more images can be acquiredby the camera 100 and transferred to the frame grabber 96 for processingby the controller 35 as described above. When the images are processedby the controller 35, a character recognition algorithm is used tointerpret the acquired image of the substrate identification 107. Inanother implementation, the substrate identification 107 includes a barcode, and the controller 35 uses a bar code reader algorithm to processthe acquired images. The substrate identification 107 as determined bythe controller 35 can be stored in a memory 108 for subsequentretrieval.

The image acquisition sensors, such as the camera 100B, also can be usedfor the detection of gross substrate defects either prior to or afterprocessing a substrate in the chambers 18-26. Referring to FIG. 14A, thetransfer arm 36 is shown with the transfer head 37 raised to an elevatedposition while the blades 72, 74 support the substrate 11. The bracket99 on which the camera 100B is mounted can be rotated between first andsecond positions, shown, respectively, in FIGS. 14A and 14B. When thecamera 100B is used to acquire images to permit the controller 35 tocorrect substrate misalignment, then the bracket 99 is its firstposition. The controller 35 can control a pneumatic actuator 125 torotate the bracket 99 from its first position to its second position.When the bracket 99 is rotated to its second position (FIG. 14B), thecamera 100B is tilted slightly so that it can acquire an image thatincludes substantially an entire surface 127 of the substrate 11. Thecontroller 35 causes the camera 100B to acquire one or more images ofsubstantially the entire substrate surface 127. The acquired images aretransferred to the frame grabber 96 so that the controller 35 canprocess the acquired images. In one implementation, an ideal image of asubstrate is stored in the memory 97, and the acquired images arecompared to the ideal image. For example, in one implementation, theintensity of each pixel in the acquired images can be compared to theintensity of a corresponding pixel in the stored ideal image. If thedifferences between the pixel intensities of the acquired images are notwithin predetermined tolerances when compared to the pixel intensitiesof the ideal image, then the substrate 11 is assumed to contain a grossor substantial defect. Such defects can include, for example, chippededges or cracks in the substrate. Further processing of the substrate 11then can be halted and the substrate can be removed from the system 10.

The cameras or other image acquisition sensors can be positioned tocapture images of the substrate 11 other than along the edges 101A, 101Bor other than at the corner 105A. Thus, for example, one or more imageacquisition sensors can be supported by flanges or brackets such thatthe image acquisition sensors are positioned adjacent the base of thetransfer arm 36. Also, the relative size of the brackets or othersupports for the image acquisition sensors can be smaller than theyappear in the accompanying drawings.

Although the foregoing implementations have been described in thecontext of the atmospheric transfer arm 36, image acquisition sensors,such as a camera 100D (see FIG. 15), can be used with other substratehandling devices as well, such as the vacuum transfer arm 38, to performone or more of the following functions: correct substrate misalignment,determine substrate identification, and perform pre-processing orpost-processing defect detection. The image acquisition sensors need notbe attached or mounted directly on the transfer arms 36, 38. Thus, forexample, the camera 100D can be mounted on the lid 130 of the transferchamber 27 to allow images to be acquired of a substrate 11 supported bythe blades 90, 92. of the vacuum transfer arm 38. The location of suchcameras with respect to some fixed reference point, however, must beknown or provided to the controller 35.

In general, images of a substrate can be captured and the position ofthe substrate can be adjusted when the substrate is transferred from onelocation to another, including to or from a load lock chamber, aprocessing chamber, or a cassette load station.

Similarly, image acquisition sensors can be incorporated into substrateprocessing systems different from the particular system described aboveto adjust substrate alignment or to perform pre-processing orpost-processing defect detection. Thus, one or more image acquisitionsensors can be incorporated into the system described in U.S. patentapplication Ser. No. 08/946,922. As shown, for example, in FIG. 16, asubstrate processing system has an aisle 210 which includes a conveyorsystem 202 and islands 204, 206 of chambers. A robot 212, which can movealong a track 208, can transfer substrates to or from the conveyor 202as well as the islands 204, 206. Image acquisition sensors can bemounted to the robot 212, for example, to correct substratemisalignment, to determine substrate identification, and to performpre-processing or post-processing defect detection. Such linear systemsare particularly suited for the processing of large substrates.

Other implementations are within the scope of the claims.

1. A substrate handling apparatus comprising: a transfer arm including asubstrate support; at least one image acquisition sensor configured toacquire images of a substrate supported by the substrate support; and acontroller coupled to the at least one-image acquisition sensor andconfigured to control the at least one image acquisition sensor toacquire the at least one image of at least two about orthogonal edgesdefining at least one corner of the substrate supported on the substratesupport, wherein the controller is further configured to receive the atleast one image acquired by the image acquisition sensor, and configuredto apply a corner detection algorithm to the at least one acquired imageto determine an initial position of the substrate, and wherein thecontroller is further coupled to the substrate support to controlmovement thereof to move the substrate to a new position based on thesubstrate's initial position.
 2. The substrate handling apparatus ofclaim 1, wherein the at least one image acquisition sensor comprises anarray of charge coupled devices.
 3. The substrate handling apparatus ofclaim 1, wherein the controller is configured to control horizontaltranslation of the substrate support to correct a misalignment of the ofthe substrate based on the substrate's initial position.
 4. Thesubstrate handling apparatus of claim 1, wherein the controller isconfigured to control angular rotation of the substrate support tocorrect a misalignment of the substrate in response to determining thesubstrate's initial position.
 5. The substrate handling apparatus ofclaim 1, further comprising a light source to enhance a quality ofimages acquired by the at least one image acquisition-sensor.
 6. Thesubstrate handling apparatus of claim 1, wherein the controller isconfigured to control the substrate support to transfer the substratefrom the new position to a substrate processing chamber.
 7. A method ofpositioning a substrate, the method comprising: supporting the substrateon a substrate support of a transfer arm; acquiring at least one imageof the substrate supported on the substrate support wherein the imageincludes at least one set of about orthogonal edges of the substrate;determining an initial position of the substrate based on the alignmentof the set of about orthogonal edges; and moving the substrate supportbased on the initial position to adjust for a misalignment of thesubstrate.
 8. The method of claim 7, wherein acquiring at least oneimage comprises capturing an image with an array of charge-coupleddevices.
 9. The method of claim 7, wherein one of the acquired imagesincludes a substrate identification, the method further comprisingperforming a character recognition algorithm to interpret the substrateidentification.
 10. The method of claim 7, further comprising:translating the substrate support vertically while the substrate issupported thereon; acquiring an image that includes substantially anentire surface of the substrate; and determining whether defects existin the substrate based on the image of substantially the entiresubstrate surface.
 11. A method of positioning a substrate, the methodcomprising: supporting the substrate on a substrate support of atransfer arm; acquiring at least one image of the substrate supported onthe substrate support wherein the image includes at least two aboutorthogonal edges defining at least one corner of the substrate;determining an initial position of the substrate based on the alignmentof the corner of the substrate; and moving the substrate support basedon the initial position to adjust for a misalignment of the substrate.12. The method of claim 11, wherein acquiring at least one imagecomprises capturing an image with an array of charge-coupled devices.13. The method of claim 11, wherein one of the acquired images includesa substrate identification, the method further comprising performing acharacter recognition algorithm to interpret the substrateidentification.
 14. The method of claim 11, further comprising:translating the substrate support vertically while the substrate issupported thereon; acquiring an image that includes substantially anentire surface of the substrate; and determining whether defects existin the substrate based on the image of substantially the entiresubstrate surface.